Field of the Invention
The present invention relates to wireless communication, and more particularly, to a method of transmitting a discovery signal of a terminal for performing device-to-device (D2D) communication, and the terminal using the method.
Related Art
Standardization works of international mobile telecommunication (IMT)-advanced which is a next generation (i.e., post 3rd generation) mobile communication system are carried out in the international telecommunication union radio communication sector (ITU-R). The IMT-advanced aims at support of an Internet protocol (IP)-based multimedia service with a data transfer rate of 1 Gbps in a stationary or slowly moving state or 100 Mbps in a fast moving state.
3rd generation partnership project (3GPP) is a system standard satisfying requirements of the IMT-advanced, and prepares LTE-advanced which is an improved version of long term evolution (LTE) based on orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission. The LTE-advanced is one of promising candidates for the IMT-advanced. A technology related to a relay station is one of main technologies for the LTE-advanced.
LTE/LTE-A provides a device-to-device (D2D) technique for performing D2D direct communication without an assistance of an evolved NodeB (eNB). Advantageously, D2D can improve system capacity, transfer rate, delay, and power consumption through a short-distance gain, a hop gain, and a frequency reuse gain. Meanwhile, when performing D2D communication, one of important procedures is to discover devices located in a short distance. For this, one device transmits a discovery signal, and other devices measure reception strength of the discovery signal to confirm whether D2D communication is possible.
Meanwhile, it may be necessary for each device for performing D2D communication to have a different period of discovery signal transmission according to a service type and a battery status. Further, if the number of devices for performing D2D communication is great, the discovery signal is transmitted preferably by decreasing a collision between the devices.
There is a need for a method of effectively transmitting the discovery signal by each of the devices for performing D2D communication, and an apparatus using the method.